For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
Garcin, Estelle, and Inez arrive in hell.
Act II
No one is willing to admit that they’ve done anything wrong. Bad faith rules the day as the three individuals try to figure out what’s going on and what they should do without owning up to their actions or making any decisions.
Act III
Everyone breaks down and admits their crimes. They all figure out that they’re in a cafeteria-style hell, as Inez puts it, and are fated to be each other’s torturers. Garcin then chooses hell, essentially for all three of them, and resigns them all to an eternity of mental torment.